Antilipemic agents

ABSTRACT

NOVEL 5-PYRAZINYL, PYRIMIDINYL AND PYRIDAZINYL TETRAZOLES AND N-OXIDES THEREOF USEFUL AS LIPID REGULATING AGENTS.

United States Patent US. Cl. 424-250 6 Claims ABSTRACT OF THE DISCLOSURENovel S-pyrazinyl, pyrimidinyl and pyridazinyl tetrazoles and N-oxidesthereof useful as lipid regulating agents.

CROSS REFERENCE TO RELATED APPLICATION This application is a division ofapplication Ser. No. 418,526, filed Dec. 15, 1964 and now US. Pat. No.3,448,107.

This invention relates generally to novel compounds which are eifectivein regulating lipid metabolism in humans. More particularly, it isconcerned with novel pyrazinyl, pyrimidin-yl and pyridazinyl tetrazolesand N- oxides thereof, and their use as antilipemic agents.

What is meant by the term regulating lipid metabolism is the ability todepress triglycerides, free fatty acids, cholesterol, lipoproteins,phospholipids, etc. in human and animal blood.

The compounds of the present invention can be represented by thefollowing structural formulas:

wherein X and X are each selected from the group consisting of H,halogen (F, Cl, Br, I), hydroxy, amino, alkyloxy, alkylthio, monoanddialkylamino, N-alkylcarbamyl, N,N dialkylcarbamyl, alkylsulfoxy,alkylsulfonyl, said alkyl groups containing from 1 to 4 carbon atoms,trifluoromethyl, trifluoromethoxy, trifluoromethylthio, carboxy,carbamyl, alkanoyloxy containing up to 4 carbon atoms, phenyl,p-chlorophenyl, p-methylphenyl and pa-minophenyl; n is a whole numberfrom 0 to 4; one of X and X is other than H; and N-oxides thereof.

The numbering system for the diazine rings, as shown in Formulae I, IIand III above, consists in selecting one nitrogen atom as the 1-positionand labeling the remaining atoms consecutively in such a manner that theshortest route, numerically, is t-aken to the second nitrogen atom. Itis obvious that for the 1,4-diazine ring system, i.e., pyrazine, thesecond nitrogen atom would be numbered as 4 regardless of the routetaken because of its symmetry.

Specific examples of such compounds include S-(6-pyrazinyl)tetrazole, 5(6 pyridizinyDtetrazole, 5 (6- ice pyrimidinyl) tetrazole, 6-S-tetrazoyl -pyrazine-N-oxide, and 5-[3-(5-butyl)pyridazinyl]tetrazole.

In accordance with the process for preparing these compounds, theappropriate cyanopyrazine, cyanopyrimidine, or cyanopyridazine compoundis condensed with sodium azide and ammonium chloride in the presence oflithium chloride. The appropriate cyano compounds are either knowncompounds or can easily be synthesized employing standard organicprocedures well known to those skilled in the art.

The condensation step itself is most desirably conducted indimethylformamide at ambient temperatures. In general, a slight excessof sodium azide and ammonium chloride, and approximately 0.01 by Weightof lithium chlo ride are used based on the cyano compound.

Recovery of the desired product from the reaction mixture is readilyetfected by any number of standard procedures known to those skilled inthe art. For instance, the procedure employed for isolating the hereindisclosed compounds is as follows: The reaction mixture is filtered toremove insoluble material and stripped free of solvent (DMF) undervacuum. The resulting residue is dissolved in a substantial amount ofwater, and the pH adjusted to about 4.0 with 'HCl solution. Theprecipitated product is filtered and a second crop is obtained from themother liquor by adjusting the pH to about 2.0 and re-filtering. Theproduct may be further purified by a recrystallization step wherein asuitable solvent, for example, water is utilized.

In addition to the procedure outlined above, several other syntheticroutes are possible. For example, the corresponding derivatives may beobtained by heating a mixture of cyano compound, acetic acid, n-butanoland sodium azide for 5 days; or by heating a mixture of cyano compoundwith hydrazoic acid in xylene in a Pyrex combustion tube.

Included within the class of compounds, represented by Formulas I, IIand III are the corresponding N-oxides. The conversion of the diazinecompounds of the invention to their respective mono N-oxides is effectedin essentially the same manner one employs to convert pyridine or itsderivatives to their respective pyridine N-oxides. The latter reactiongenerally consists of oxidizing the pyridine compound with a hydrogenperoxide solution in a suitable reaction medium, for example, glacialacetic acid. In a similar manner, the mono N-oxides of the 5-pyrazinyl,pyrimidinyl, and pyridazinyl tetrazoles of the present invention havebeen prepared. A- procedure which has been found to be satisfactory isas follows: A mixture containing S-pyrazinyl, pyridazinyl, orpyrimidinyl tetrazole compound, glacial acetic acid, and 30% hydrogenperoxide is heated for approximately 24 hours at a temperature fromabout 0 C. to about C. The mixture is subsequently cooled, diluted witha large volume of ether, and the precipitated product is filtered. Topurify further, said product may be crystallized from a suitablesolvent, for example, water. Since the above compounds possess twonitrogens susceptible to attack, only a slight molar excess of hydrogenperoxide is utilized. Preferential attack is on one of the two nitrogensin the six-membered ring.

Since the compounds of this invention are amphoteric in nature, they canbe converted to either acid or base addition salts by treating saidcompounds with a substantially equimolar amount of a chosen acid or basein an aqueous solution or in a suitable organic solvent such as methanolor ethanol. When such salts are to be used for human consumption, eitherorally or parenterally, the acids or bases which are used to prepare thepharmaceutically acceptable addition salts must, of course, be thosewhich necessarily form non-toxic acid addition salts. Examples of acidswhich provide pharmaceutically acceptable anions are hydrochloric,hydrobromic, hydroiodic, nitric, sulfuric or sulfurous, phosphoric,acetic, lactic, citric, tartaric, oxalic, succinic, maleic, gluconic,and p-toluene sulfonic.

The bases which are used to prepare the pharmaceutically acceptable basesalts of the tetrazoles of this invention are those which form non-toxicsalts containing pharmaceutically-acceptable cations, such as the alkalimetal, alkaline-earth metal, ammonium or water-soluble amine additionsalts like the lower alkanol-ammonium and other base salts with organicamines which are compatible with the human system. Preferred members ofthis group include the sodium, potassium, magnesium, calcium andethanol-ammonium salts.

The tetrazole derivatives and N-oxides thereof of this invention can beadministered either alone or preferably in combination with apharmaceutically acceptable inert carrier in the form of tablets,capsules, lozenges, troches, hard candies, powders, sprays, aqueoussuspensions or solutions, injectable solutions, elixirs, syrups, and thelike. Such carriers include solid diluents or filters, sterile aqueousmedia and various non-toxic organic solvents. Moreover, the oralpharmaceutical compositions of this invention may be suitably sweetenedand flavored by means of various agents of the type commonly employedfor just such a process.

For purposes of parenteral administration, solutions or suspensions ofthe herein described tetrazole derivatives in sesame or peanut oil or inaqueous propylene glycol solutions can be employed, as well as sterileaqueous solutions of the corresponding water-soluble addition saltspreviously enumerated. These particular solutions are especially suitedfor intramuscular and subcutaneous injection purposes. The aqueoussolutions, including those of the addition salts dissolved in puredistilled water, are additionally useful for intravenous injectionpurposes provided that their pH be properly adjusted beforehand. Suchsolutions should also be suitably buffered, if necessary, and the liquiddiluent first rendered isotonic with sufiicient saline or glucose.

When administered to humans orally or parenterally, the effectiveaverage daily dose is suitably between about 0.5 g. per day and about 3g. per day. The dosage can be taken at one time or divided dosages canbe taken at different times during the day. On a body-weight basis, adosage of about 73 to about 440 mg./kg. per day is appropriate.

The physician will determine the dosage which will be most suitable foran individual patient and it will vary with the age, the weight andresponse of the particular patient. The above dosages are exemplary ofthe average host. There can, of course, be individual cases where higheror lower dosage ranges are merited, and such are within the scope ofthis invention.

The term lipids is used here in the broad sense, covering triglycerides,cholesterol, phospholipids and free fatty acids. It is generallyaccepted that abnormalities in lipid metabolism, frequently indicated byelevated blood lipid levels, are closely associated withatherosclerosis, with cardivascular disease, and with derangements ofcarbohydrate metabolism, e.g. diabetes. Drugs which will lower lipidlevels can therefore be expected to be useful in the treatment of thesediseases, and of others in which lipid metabolism is abnormal.

The verification that the herein disclosed tetrazole derivatives areeffective lipid regulating agents is established by in vivo evaluation.The procedure for the in vivo evaluation which determines the timecourse of mobilization of free fatty acids is as follows: An intravenousdose of mg./kg. of test compound is administered to 2 or more dogs.Blood samples are withdrawn for controls and at /2, 1 hour and hourlythrough an eight hour period. Plasma free fatty acid levels are measuredand expressed as Eq. FFA/l of plasma and results are tabulated in termsof percent fall of free fatty acids.

The usefulness of the herein disclosed compounds may be also evident inother phases of abnormal lipid metabolism, the latter possiblyaccounting for the clinical problems in diabetes, pancreatitis, coronaryheart disease, cerebrovascular disease, etc. Hence, the ability oftetrazoles of the instant invention to decrease or regulate lipidmetabolism might find utility in the treatment of the above saiddiseases.

The following examples are provided by way of illusration and should notbe interpreted as limiting the invention, many variations of which arepossible without departing from the spirit or scope thereof.

EXAMPLE I 5-(6-pyrazinyl)tetrazole A mixture of 6-cyanopyrazine (235 g.,2.24 M), sodium azide g., 3.0 M), ammonium chloride (162 g., 3.0 M),lithium chloride (3.0 g.) and dry dimethylformamide (1500 ml.) isstirred for 42 hours. On completion of said period, insoluble materialis filtered and the mother liquor stripped of dimethylformamide. To theresulting residue is added 4000 ml. of water and the pH adjusted to 4.0with an HCl solution. The product 5-(6- pyrazinyl)tetrazole is obtainedby filtration and a second crop is obtained by adjusting the pH of thefiltrate to 2.0 and re-filtering. The combined crop yields a substantialamount of product, M.P. ISO-182 C.

Analysis.Calcd. for C H N (percent): C, 40.54; H, 2.72; N, 56.74. Found(percent): C, 40.43; H, 3.08; N, 56.23.

EXAMPLE II 5-( 6-pyrimidinyl)tetrazole 5-(6-pyridazinyl)tetrazole Theprocedure of Example I is repeated for the preparation of5-(6-pyridazinyl)tetrazole wherein a stoichiometric equivalent amount offi-cyanopyridazine is used in place of G-cyanopyrazine and substantiallythe same results are obtained.

EXAMPLE IV The procedure of Example I is repeated for the preparation ofthe fololwing compounds wherein a stoichiometric equivalent amount ofthe appropriate cyano compound is used in place of 6-cyanopyrazine andthe corresponding products are obtained in substantial amounts.

Cyano compound Product o. 5-[5-(3-amino)pyridazinyHtetraz e.3,6-diehloro-5-eyanopyridazine 5-[5 (3,6-dicl1Ioro)pyridazinyl] tetrazolE-eyanopyridazine. S-cyanopyrimidine. 2-cyanopyrimidine.3-amino-5-cyanopyridazine.

e. 5-methoxy-6-eyanopyridazine 5-[6-(5-methoxy)pyridazinyl] tetrazole4-butyroxy-6-cyanopyridizine 5-[6(4-butyroxy)pyridazinyl] tetrazole ra2-p-phlorophenyl-5-cyanopyrimi- 5-[5-(2-p-ehlorophepyl) pyrimidlue.dinyl1tetrazole. 4-phenyHi-eyanopyrimidine 5-[6-(4-phenyl)pyrimidinyl]tctrazole e. Bmethylsulfonyl-5-cyanopyrazlne...6-[5-(3-methylsulfonyl)pyrazlnylltetrazole.

Product 5-[5-(3-methylsu1foxy)pyrazinyl] tetrazole.5-[6-(3-methylamino)pyridazinyl] tra ol Cyano compound3-methylamino-G-cyanopyridazine large volume of ether. The precipitate,6-(5-tetrazoyl) py-razine-N-oxide, which forms is filtered andrecrystallized from water to give a substantial amount of product.

te Z 5 EXAMPLE VI4-N,Ndimkethylcarbamwl-6-cyanofi-lfi-(i-NN-dimethylcarbamy pyrldazlne.Fyndazinyfltetrazole. 6-(S-tetrazoyl)pyrimidine-N-oxide3-trlfluoromethyl-5-cyanopyrid- 5- 5-(3-ll;lrfltuororlnethyl)pyridazine. aziny e IELZO e. 5 b1 1ty1carbamy1 2cyampyrinm 5 [2:(5 buty1carbamy1)pyrimb The procedure of Example V 1srepeated for the prepdine. d1nyl]tetrazole. matron of6-(S-tetrazoyl)pyrimidine-N-oxide with comfi-carboxyQrcyanopyrimidme5-[t2-flcarlboxy)pyrlmldinyl] 10 pal-able results e razo 8.fi-p-chlorophenyl-2-cyanopyriml- 5-[2-(5-p-chlorophenyl)pyrimi- EXAMPLEVII dine. dinyHtetrazole. 4,5-dlaoetoxy-2cyanopyrnmdmefi-[tfigzgzacetoxw pynmidinyl] 6 s tetrazoyl PyridaZine N 0Xide4-pmethylphenyl-2-cyanopyrlmi- 5[2-(4-p-methylphenyl)pyrimi- 2 gn ie m 61 am 5 $1 1 te tr azor imidm 1 The procedure of Example V is repeatedfor the prep- Y m Wampyr g g am Y1 aration of6-(S-tetrazoyl)pyridazine-N-oxide with com- 2,3-dibromo-6-eyanopyrazinefi-ltfi-ilfi-dibromwpyrazinyl] parable results.

e razo e. 2-fiuoro-5-cyanopyrazine 5-[5'(2-fiuoro)pyrazinyfltetrazole.EXAMPLE VIII Z-trifiuoromethoxy-fi-cyanopyrazme.5-[6-(2-trifluoromethoxy)pyrazlnyl] tetrazo1e. The N-oxides of thecompounds tabulated in Example ;*E figfiggg gg IV are prepared followingthe procedure described in line. 4-phenyl-6-cyanopyridazme5-[i-t(4-ph1enyl)pyrldazinyl] Example V Wlth comparable results.

e IEZO e. 4N,N dibutylcarbamyl-fi-cyano- 5-[6-(4'N,N-dibutylcarbamyl)pyridazine. pyridazinylltetrazole. EXAMPLE DC3-N-ethy1carbamyl-5-cyanopyr- 5[5i(3-liIt-etthyl iarbamy1)pyraazme. Z HYe razo e. t 4-triglfiloromethylthio fi-cyanopyrld-5-[6-(iigriiluorfiniethylthim 35 -11 5 P s g pgg dlslcloged 1 3 y be aze. py azmy e razo e. ver e 0 en am a ition sa ts yt e following general5- yridazinylacetonitrile fi-(fi-pyrldazinylmethyl)tetrazole.g-gyridamyllvalemmtiglei g-gg-pyrida aipyllg fiygEels- 1 procedure. Ta@(1 nlithanofiz golutionhcontaimng the dia. -pyrimi my PI'Opl'lOll r e.--py i mye y e razo e. zine compoun 1 is a e a stoic iometric equivalent6- irnidiny1butyr0nitri1e 6-(6-pyrimidinylpropyl)tetrazolevb-ggunidirgrlacetongrlilen g-E ri idi 1 1m 1 t t i amountI of asuitilgle ac fd. The resulting solution is sub- G-pyraziny utyroni ie-pyrazmv p ps e raz sequent y strippe ree 0 so vent and the precipitateacid -but -5- 'dazin 1 r0 rio 6- 5- 3-butox idazin leth l 3 mt Y P Pltemole. mm i y] addition salt, is filtered and dried. Other suitablesolvents, 4-b gzyg ofi-py v -igggfi g gggw for example, ethanol, wateror mixtures thereof may be H l'l I 5 i g fi g a p i gig. g t t l n t t lUtlllfifli. The folowmg 201d bQddltlOIl salts are typical exy p op o r W32 Y 9 m0 amp es prepare using t e a ove said procedure and sub-LN,N-dibutylcarbamyl-o-pyrimi- 5-[6-(4N,N-dibutylcarbamyl)dinylbutyronitrile. pyrimidinylburyfltetrazole. 35 Stantlal ylelds ofProduct are obtall'led- 3-butylsulfonyl-6-pyrazinylaceto-5-[6-(3-butylsulionyl)pyrazinylnltrile. methyfltetrazole. EXAMPLE X3-methylcarbamyl-fi-pyridazlnyl- 5[5 -(3-methylcarbamyl)pyridaa iii iinos d 1 5 i i id '0 010 31111 1 aziny 0 OlO ammo pyr flprqprmonmne PYTI zinylemyntetmoler The hydrochloride, hydrobromide, and hydroiodideacid 3,4-d1propyl-5-cyanopyr1dazme 5-[5t(3,4-d1propyl)pyrldazinyl] 0addltion salts of those compounds enumerated in Exam- G razo 9.5-earboxy-6cyan0pyrhnidine 5-[ s-s cagboxy)-pwlmidinyll gi g ggfig gggfiggg i g Nepal-$1 er zo e. W1 com ara 6ISU S. Zbromo-Scyanopyrimidine5-[l:i-2-br 1)mo)-pyrlm1d1nyl] P P 8 razo e.2-butyl-4-methoxy-6-pyrimidinyl- 5-[6- (2-buty1-4methoxy)pyriml- EXAMPLEXI butyronltrileimw 1 1 5 gizizylllprgrpyfltetrazoleim 1b t 1 g fi: my gf y u y] The class of compounds disclosed herein may be con- Y- y opy-lg f ig l l verted to their base addition salts by the followinggeneral procedure. To a water solution containing the diazine Dlazinecompound Acid Acid addition salt 5-(6-pyrazinyl)tetrazole H01-..5-(6-pyrazinyl)tetrazo1e hydrochloride.

5-(6-pyrimidiny1) tetrazole. 5-(6-pyridaziny1) tetrazole.

6- (5-tetrazoy1) pyraziue-N-oxide 6-(5-tetrazoyl)pyrimidine-N-omdePhosphoric acid 6-(5-tetrazoyl)pyrimidine-N-oxide phosphate.

EXAMPLE V 6-(S-tetrazoyl)pyrazine-N-oxide A mixture of 5-6-pyrazinyl)tetrazole (37.0 g. 0.25 M), glacial acetic acid (200 ml.)and 30% hydrogen peroxide (30 ml.) is heated at 90 C. for 24 hours.After this time period, the reaction mixture is cooled and diluted witha HBr fi-(fi-pyn'midinyl)tetrazole hydrobromide. S-(G-pyridazinyl)tetrazole hydroiodine. 6-(5-tetrazoyl)pyrazine-N-oxide acetate.

compound (1 M) is added a stoichiometric equivalent amount of a suitablebase. The resulting solution is subsequently stripped free of solventand the precipitate, base addition salt, is filtered and dried. Thefollowing base addition salts are typical examples prepared using theabove described procedure and substantial yields of product areobtained:

Diazine compound Base addition salt 5-(6-pyrazinyl) tetrazole.fi-(fi-pyrimidinyl)tetrazole 5-(6-pyridazinyl) tetrazole6-(5-tetrazoyl)pyrazine 6-(5-tetrazoyl) pyrimidine-N-oxi6-(5-tetrazoyl)pyridazine-N-oxide.

Sodium salt of 5-(6-pyrazinyDtetrazole.

Potassium salt of E-(G-pyrimidinyl)tetrazole.

Calcium salt of 5-(6-pyridazinyl)tetrazole.

. Magnesium salt of 6-(5-tetrazoy1)pyrazine-N-oxide.

onium salt of 6-(5-tetrazoyl)pyrimidine-Nbxide.

hydroxide. Mono ethanolamine. Mono ethanolamine salt ofG-(S-tetrazoyl)pyridazine-Nbxide.

7 EXAMPLE XII The sodium, potassium, calcium, magnesium and ammoniumsalts of those compounds enumerated in Example IV and mono N-oxidesthereof are prepared following the procedure of Example XI withcomparable results.

EXAMPLE XIII The following pharmacological test procedure is used tomeasure the hypolipemic effects (in vivo assay) of 5-(6-pyrazinyl)tetrazole. An intravenous dose of 10 mg./ kg. of testcompound is administered to 2 or more dogs and blood samples arewithdrawn periodically. Plasma free fatty acid levels are measured andresults are expressed as percent fall of free fatty acids.

Percent maximum fall Compound: of free fatty acids5(6-pyrazinyl)tetrazole 60 Thus, the ability of 5-(6-pyrazinyl)tetrazoleto effective- 1y lower free fatty acid levels is clearly indicated.

EXAMPLE XIV on NH on NH N 2) I J*( 2) wherein X and X are each selectedfrom the group consisting of H, halogen, hydroxy, amino, alkyloxy,alkylthio, monoand dialkylamino, N-alkylcarbamyl, N,N-dialkylcarbamyl,alkylsulfoxy, alkylsulfonyl, said alkyl groups containing from 1 to 4carbon atoms, trifluoromethyl, trifluoromethoxy, trifiuoromethylthio,carboxyl, carbamyl, alkanoyloxy containing up to 4 carbon atoms,

phenyl, p-chlorophenyl, p-methylphenyl and p-aminophenyl; n is a wholenumber from 0 to 4; and the N-oxides thereof.

2. The method of claim 1 wherein said compound is5-(6-pyrazinyl)tetrazole.

3. The method of claim 1 wherein said compound is5-(6-pyridazinyl)tetrazole.

4. The method of claim 1 wherein said compound is5-(6-pyrimidinyl)tetrazole.

5. The method of claim 1 wherein said compound isS-(S-pyrimidinyl)tetrazole.

6. A method of lowering elevated blood lipid levels in humans sufferingfrom hyperlipemia which comprises orally administering apharmaceutically effective amount of a pharmaceutically acceptableaddition salt of a compound selected from the group consisting of thoseof the formulae:

(CH n 1TH (C1191. NH

N l W References Cited UNITED STATES PATENTS 9/1958 Elpern 260308.4

OTHER REFERENCES Holland: J. Med. Chem., Vol. 10, 1967, pp. 149-153.

STANLEY J. FRIEDMAN, Primary Examiner A. P. FAGELSON, Assistant ExaminerUS. Cl. X.R. 424-251

